Recent trends in the access communications market show that data rates up to 100 Mb/s which are provided by VDSL systems using Vectoring as defined in ITU-T Recommendation g.993.5 are not sufficient and bit rates up to 1.0 Gb/s are required for some applications. This can currently only be achieved in a wire-based system if copper pairs connecting customer premises equipment (CPE) as short as 50-100 m. Operation using so short loops requires installation of many small street/MDU (multi dwelling unit) cabinets called Distribution Points (DP) that intends to serve a very small number of customers, e. g. 16 or 24 and is connected to the backbone via fiber (fiber to the distribution point FTTdp).
Vectoring may be used in systems operating from a DP to reduce far-end crosstalk (FEXT), which is absolutely necessary to obtain high bit rates. To improve energy efficiency and to reduce hardware complexity, synchronized time division duplexing (S-TDD) is used for FTTdp.
DPs shall allow very flexible installation practices: they should be light and easy to install on a pole or house wall, or basement, without air-conditioning. The most challenging issue for these flexible connection plans is providing DPs with power. The only solution found is so-called “reverse feeding” when the equipment of the DP is fed by the connected customer. The requirement of reverse power feeding and the small size of the DP implies substantial restrictions on the power consumption of the DP.
Therefore, reducing the power consumption of DPs would be desirable.
Discontinuous operation has been proposed to save power in FTTdp communication. However, discontinuous operation adds some complexity to a line joining process and reduces the achievable bit rates.
Reducing peak bit rates on the other hand means that the transmission time to provide a given data rate increases, and this reduces the power savings.
Maintaining stability, bit error rates and transmit power constraints when lines sharing one cable binder discontinue transmission may result in performance degradation in conventional approaches.